In order to reduce emissions of air pollutants, and especially Nitrogen Oxides (NOx) in the United States, the Environmental Protection Agency (EPA) is steadily tightening emissions standards for the power generation industry, including gas, oil, and coal-fired power plants. A progressive method to produce power is by gasification of coal and/or other carbonaceous materials, resulting in production of a hydrogen-containing fuel gas, followed by combustion of this fuel in a gas turbine. This method allows effective production of power, and allows reduction of emissions of several air pollutants such as CO, volatile organic compounds (VOCs), etc. into the ambient air. However, combustion of hydrogen or hydrogen-containing fuel in a gas turbine at high efficiency leads to a significant amount of NOx in the exhaust gases that must be removed.
Existing NOx reduction technologies include selective catalytic reduction (SCR) as an efficient way to reduce emissions of NOx to low levels. Various reducing agents can be used in SCR systems, including hydrocarbons, hydrogen, ammonia, urea, etc. Ammonia is the most efficient reducing agent at reducing NOx emissions to low levels. Urea also produces ammonia by its decomposition in the process of NOx reduction. However, ammonia has several disadvantages:                Ammonia is toxic, so its storage requires strong safety measures. Accidental release of ammonia from a storage tank is a hazard.        Ammonia slipping through the SCR process without reacting can reach levels of 5-10 ppm in the final exhaust, which is harmful to the environment.        Delivery of ammonia to a power generation station is hazardous.        Ammonia is not fully effective as a NOx reducing agent until the temperature in the SCR reactor reaches about 260-300° C. or higher, so NOx is not effectively reduced by ammonia during start-up cycles of power generation units, when exhaust temperatures are lower.        